Constant velocity universal joint

Abstract

To provide a constant velocity universal joint capable of prolonging a service life of a boot, further effectively preventing grease from flowing out to the outside, and maintaining lubrication performance over a long period of time.SOLUTION: A shaft comprises a sleeve inner ring that is internally fitted into the shaft so as to be slidable in an axial direction of the shaft, and a sleeve outer ring that is fixed to an inside joint member and externally fitted onto the shaft. A gap part is formed between the sleeve outer ring and the opposing shaft, into which the sleeve inner ring is slidably fitted. The boot inner fitting part of the sleeve inner ring remains fitted in the gap part, and the sleeve outer ring and the sleeve inner ring always have an overlap portion therebetween.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a constant velocity universal joint, and more particularly to a constant velocity universal joint for industrial machinery used in steel, paper, chemical plants, and the like. [Background technology]

[0002] A power transmission mechanism used in the rotation transmission section of industrial machinery comprises a pair of constant velocity universal joints spaced apart in the axial direction and an intermediate shaft connecting the two constant velocity universal joints. Constant velocity universal joints are classified into fixed type constant velocity universal joints that allow only angular displacement, and sliding type constant velocity universal joints that allow not only angular displacement but also axial displacement.

[0003] However, since a sliding type constant velocity universal joint allows not only angular displacement but also axial displacement, the sealing device (e.g., a boot) that seals the opening of the outer joint member will also be displaced in response to these displacements.

[0004] That is, as shown in FIG. 9 , a conventional sliding type constant velocity universal joint includes an outer joint member 4 having a plurality of linear track grooves 3 formed along the axial direction on its cylindrical inner peripheral surface, an inner joint member 6 having a plurality of linear track grooves 5 formed along the axial direction on its spherical outer peripheral surface in pairs with the track grooves 3 of the outer joint member 4, a plurality of balls 7 as torque transmission members interposed between the track grooves 3 of the outer joint member 4 and the track grooves 5 of the inner joint member 6 to transmit torque, and a cage 8 interposed between the cylindrical inner peripheral surface of the outer joint member 4 and the spherical outer peripheral surface of the inner joint member 6 to hold the balls 7.

[0005] Each outer joint member 4 comprises a cylindrical main body 9 having track grooves 3 formed on its cylindrical inner circumferential surface, and a flange 10 provided on one opening side of the cylindrical main body 9. The other opening of the cylindrical main body 9 is closed by a boot 11. The boot 11 comprises a large diameter portion (one opening) 11a, a small diameter portion (the other opening) 11b, and a bellows portion 11c connecting the large diameter portion 11a and the small diameter portion 11b. The large diameter portion 11a is fitted onto a boot attachment portion 12 having a circumferential groove at the other opening of the cylindrical main body 9, and in this state is fastened by a boot band 13.

[0006] The shaft S is provided with a boot attachment portion 14 having a circumferential groove, and the small diameter portion 11b of the boot 11 is fitted onto this boot attachment portion 14, and in this state, the boot is tightened by a boot band 13. A retaining ring 17 is attached to the open end of the inner peripheral surface of the outer joint member 4 to prevent the internal parts P (the inner joint member 6, cage 8, balls 7, etc.) from coming off. That is, a circumferential groove 16 is provided on the open side of the inner diameter surface of the cylindrical main body 9 of the outer joint member 4, and a retaining ring 17 is attached to this circumferential groove 16.

[0007] A male spline 15d is formed on the end of the intermediate shaft (shaft) S, and the male spline 15d is fitted into the axial hole of each inner joint member 6. A female spline 6a is formed on the inner diameter surface of the axial hole of each inner joint member 6. Therefore, when the male spline 15d of the shaft S is fitted into the axial hole of each inner joint member 6, it meshes with the female spline 6a of each inner joint member 6.

[0008] A pair of retaining rings 21, 22 is attached to each male spline 15d at both ends of the shaft S. That is, circumferential grooves are formed on the joint inner side and joint opening side of the male spline 15d, and a retaining ring 21, 22 is fitted into each circumferential groove. Therefore, the inner joint member 6 is interposed between the pair of retaining rings 21, 22. This prevents the shaft S from coming off the inner joint member 6. Therefore, the internal part P is reciprocatable within the outer joint member 4 in the direction of arrow X (axial direction).

[0009] In this configuration, as shown by the solid line in Figure 9, when the ball 7 of the internal part P slides from the neutral state (state where the boot is not expanded or contracted) in which the internal part P is disposed in the center of the outer joint member 4 to the position shown by the imaginary line 7a, that is, when the internal part P slides toward the rear of the joint, the shaft S also slides toward the rear of the joint. When the shaft S slides toward the rear of the joint, the small diameter portion 11b of the boot 11 fixed to the shaft S also moves toward the rear of the joint. As a result, the boot 11 is compressed.

[0010] Furthermore, when the ball 7 of the internal part P slides from the neutral state (a state in which the boot is not stretched or contracted) in which the internal part P is disposed in the center of the outer joint member 4 to the position indicated by the imaginary line 7b, that is, when the internal part P slides toward the joint opening side, the shaft S also slides toward the joint opening side. When the shaft S slides toward the joint opening side, the small diameter portion 11b of the boot 11 fixed to the shaft S also moves toward the joint opening side. As a result, the boot 11 enters a stretched state.

[0011] Therefore, the sliding of the internal part P causes the boot to expand and contract, which may shorten the lifespan of the boot, posing a durability problem. In other words, durability (long life) is required of boots.

[0012] Conventionally, fixed type constant velocity universal joints that have an increased lifespan for boots have been configured as disclosed in Patent Documents 1 and 2. Patent Document 1 discloses a structure that includes an outer joint member having an opening, and an inner joint member that transmits torque between the outer joint member and the inner joint member while allowing angular displacement via a torque transmission member, a shaft member is connected to the inner joint member so as to be displaceable in the axial direction, and an expandable boot that closes the opening of the outer joint member is stretched between the outer joint member and the shaft member.

[0013] In Patent Document 1, a tubular member is fitted onto the shaft member so as to be axially slidable, one end of the tubular member is fixed to the inner joint member, and the other end of the tubular member is fixed to the small-diameter end of the boot. Therefore, even if the shaft member is displaced angularly and axially relative to the inner joint member, the boot expands and contracts in response to the angular displacement of the shaft member, but does not expand and contract in response to the axial displacement of the shaft member, so the natural length of the boot is maintained. In other words, the natural length of the boot is maintained, thereby extending the life of the boot.

[0014] In Patent Document 2, the boot is designed to maintain its natural length without expanding or contracting due to axial displacement of the shaft member. In this case, a pair of sleeves are provided in the boot, allowing the shaft to slide in the axial direction, and a spring member is interposed between the sleeves. In other words, when the shaft member is displaced in the axial direction, the axial distance between the pair of sleeves is maintained constant, thereby preventing the boot from expanding or contracting.

[0015] Therefore, when considering applying the configurations of Patent Document 1 and Patent Document 2 to a sliding type constant velocity universal joint, using a spring member as in Patent Document 2 would increase the number of parts and make assembly workability poor, so the use of a spring member was not adopted.

[0016] For this reason, a power transmission mechanism using a constant velocity universal joint as shown in Figure 6 can be adopted as a configuration that eliminates expansion and contraction of the boot. In this case, the power transmission mechanism comprises a pair of sliding type constant velocity universal joints arranged axially apart, and an intermediate shaft that connects both constant velocity universal joints. Note that hatching indicating cross sections has been omitted to simplify the drawing.

[0017] Both sliding type constant velocity universal joints are double offset type sliding type constant velocity universal joints 1 and 2. Each sliding type constant velocity universal joint 1 and 2 in this case has the same configuration as that in Fig. 9 , and the same components are designated by the same reference numerals, and their description will be omitted. The intermediate shaft (shaft) S comprises an intermediate large-diameter shaft portion 15a and end-side small-diameter shaft portions 15c connected to both axial ends of the intermediate large-diameter shaft portion 15a via tapered portions 15b. A male spline 15d is formed on the end of each small-diameter shaft portion 15c, and the male spline 15d is fitted into the shaft hole of each inner joint member 6. A female spline 6a is formed on the inner diameter surface of the shaft hole of each inner joint member 6. Therefore, when the male spline 15d of the shaft S is fitted into the shaft hole of each inner joint member 6, it meshes with the female spline 6a of each inner joint member 6.

[0018] 6 shows a state in which the internal part P is slid (moved) toward the inner side of the joint (contracted state), and from this state the internal part P can be displaced to a state in which it is slid (moved) toward the joint opening side (extended state), or conversely, it can be displaced from the extended state to the contracted state. At this time, the shaft S also slides (moves) toward the inner side of the joint relative to the outer joint member 4 together with the internal part P, and also slides (moves) toward the joint opening side.

[0019] In this case, a sleeve 25 is provided which is fitted inside the boot 11 with the end of the small diameter portion of the boot 11 interposed between the small diameter portion 11b of the boot 11 and the outer diameter surface of the shaft S. The shaft S is inserted (fitted) into the sleeve so as to be slidable in its axial direction.

[0020] 7(a) (contracted state) to the state shown in Fig. 8(a) (expanded state), the internal part P moves from the rear side of the joint to the joint opening side, and the shaft S slides in the direction of arrow A relative to the sleeve 25. However, the small diameter portion 11b of the boot 11 does not move.

[0021] 8(a) to the state shown in FIG. 7(a), when the internal part P slides from the joint opening side to the rear side of the joint, causing the shaft S to slide in the direction of arrow B, the shaft S will slide in the direction of arrow B relative to the sleeve 25. Therefore, even in this case, the small diameter portion 11b of the boot 11 will not move.

[0022] 6, by disposing the sleeve 25, the boot does not expand or contract in association with axial displacement of the shaft S, and the natural length of the boot 11 is maintained. In other words, the natural length of the boot 11 is always maintained, thereby extending the life of the boot. [Prior art documents] [Patent documents]

[0023] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-211018 [Patent Document 2] Japanese Patent Application Publication No. 2023-36579 Summary of the Invention [Problem to be solved by the invention]

[0024] Incidentally, the interior of the joint and the boot are filled with grease. Therefore, in the contracted state shown in Fig. 7(a), grease G shown in Fig. 7(b) adheres to the portion of the shaft S inside the boot that is exposed from the sleeve 25. When the boot is expanded from this state to the expanded state shown in Fig. 8(a), the other end of the sleeve 25 (the end on the internal part side) presses against (fits into) the grease G, as shown in Fig. 8(b).

[0025] In this case, the shaft S is axially slidable relative to the sleeve 25, resulting in a clearance fit between the shaft S and the sleeve 25. This creates a small gap between the outer diameter surface of the shaft S and the inner diameter surface of the sleeve 25. Therefore, when grease G is pressed (fitted), it will enter this gap. If grease G enters the gap in this way, there is a risk that the grease G will be discharged to the outside of the boot 11, as shown in Figures 8(a) and 8(b). If the grease G is discharged to the outside of the boot 11, it may scatter onto surrounding components. If the amount of grease in the fitting body or the boot becomes low, this may result in poor lubrication of the fitting and reduce its durability. Furthermore, depending on the intended use, periodic grease replenishment and labor such as wiping off the grease G may be required.

[0026] Therefore, in consideration of the above problems, the present invention provides a constant velocity universal joint in which the boot does not displace even when internal parts slide, thereby extending the life of the boot, and furthermore, effectively preventing grease from leaking to the outside, thereby maintaining lubrication performance for a long period of time. [Means for solving the problem]

[0027] The constant velocity universal joint of the present invention comprises an outer joint member, an inner joint member, and a torque transmission member interposed between the outer joint member and the inner joint member, an internal part having the inner joint member and the torque transmission member is housed in the outer joint member so as to be slidable in the axial direction, a shaft is connected to the inner joint member of the internal part, one open end is attached to an opening of the outer joint member, and the other open end is attached to the shaft so that the inside of the joint is sealed, and the end opposite the internal part is in contact with the inner diameter part of the other open end of the boot and the shaft. The sleeve comprises an inner sleeve ring which is inserted into the boot and is interposed between the outer diameter surface of the boot and into which the shaft is fitted so as to be able to slide in the axial direction, and an outer sleeve ring whose end opposite the inner sleeve ring is fixed to the inner joint member of the internal part and into which the shaft is fitted, and a gap is formed between the outer sleeve ring and the shaft facing it, into which the inner sleeve ring is fitted so as to be able to slide, and the boot inner fitting portion of the inner sleeve ring is maintained fitted in the gap, so that the outer sleeve ring and the inner sleeve ring always have an overlapping portion.

[0028] According to the constant velocity universal joint of the present invention, since the shaft is connected to the inner joint member of the internal part, when the internal part reciprocates between the joint opening side and the joint inner side relative to the outer joint member, the shaft also reciprocates in response to this reciprocating movement. However, since the shaft is slidably fitted into the inner ring of the sleeve, the small diameter portion (the other open end) of the boot does not slide in response to the sliding of the shaft, and no displacement of the boot occurs.

[0029] The shaft inside the boot is fitted into the outer ring of the sleeve on the side of the internal component, and the small diameter portion of the boot (the other open end) is fitted into the inner ring of the sleeve, and the outer ring and the inner ring of the sleeve always have an overlapping portion. This prevents the shaft inside the boot from being exposed inside the boot, and prevents grease from getting between the outer ring of the sleeve and the shaft or between the inner ring of the sleeve and the shaft, effectively preventing grease from leaking out of the boot.

[0030] A circumferential projection projecting outward may be provided on the edge of the outer sleeve ring facing the inner sleeve ring. By providing the circumferential projection in this manner, the circumferential projection serves as a so-called grease return, effectively preventing grease adhering to the outer sleeve ring from flying into the boot due to centrifugal force and leaking out of the boot.

[0031] A seal member for sealing the gap between the outer sleeve ring and the inner sleeve ring may be disposed on the edge of the outer sleeve ring on the inner sleeve ring side. By configuring in this manner, grease will not enter between the outer sleeve ring and the inner sleeve ring, and will effectively be prevented from leaking out of the boot. [Effects of the Invention]

[0032] In the present invention, the small diameter portion (the other open end) of the boot does not slide as the shaft slides, and the boot is not displaced. This allows for a longer boot life. Furthermore, grease is effectively prevented from leaking out of the boot, preventing it from scattering onto surrounding components or reducing the amount of grease in the joint body or boot. This allows for excellent lubrication performance to be maintained over the long term, and greatly reduces the possibility of poor joint lubrication causing a loss of durability. [Brief explanation of the drawings]

[0033] [Figure 1] 1A and 1B show a constant velocity universal joint according to the present invention, in which FIG. 1A is a cross-sectional view in a contracted state, and FIG. 1B is a cross-sectional view in an extended state. [Figure 2] 1 is a cross-sectional view showing a power transmission mechanism using a constant velocity universal joint according to the present invention. [Figure 3] 10A and 10B show a state in which grease is attached to the outer ring of the sleeve in a contracted state, where FIG. 10A is a cross-sectional view and FIG. 10B is an enlarged view of a main part. [Figure 4] 10A and 10B show a state in which grease is attached to the outer ring of the sleeve in an extended state, where FIG. 10A is a cross-sectional view and FIG. 10B is an enlarged view of the main part. [Figure 5]10A and 10B show a constant velocity universal joint of a modified example, in which FIG. 10A is a cross-sectional view in a contracted state, and FIG. 10B is an enlarged cross-sectional view of a main part in the contracted state. [Figure 6] 10 is a cross-sectional view of a power transmission mechanism using a sliding type constant velocity universal joint with a non-expandable boot. FIG. [Figure 7] 7A and 7B show a constant velocity universal joint used in the power transmission mechanism of FIG. 6, in which FIG. 7A is a cross-sectional view in a contracted state, and FIG. 7B is an enlarged cross-sectional view of a main part in the contracted state. [Figure 8] 7A and 7B show a constant velocity universal joint used in the power transmission mechanism of FIG. 6, in which (a) is a cross-sectional view in an extended state, and (b) is an enlarged cross-sectional view of a main part in the extended state. [Figure 9] FIG. 1 is a cross-sectional view showing a conventional sliding type constant velocity universal joint. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

[0035] 2 shows a power transmission mechanism using a constant velocity universal joint (sliding type constant velocity universal joint) according to the present invention, and includes a pair of sliding type constant velocity universal joints 31 (31A, 31B) spaced apart in the axial direction, and an intermediate shaft (shaft) S connecting the two constant velocity universal joints. To simplify the drawing, hatching indicating cross sections has been omitted. The pair of sliding type constant velocity universal joints 31A, 31B have the same configuration.

[0036] As shown in FIG. 1 , the pair of sliding type constant velocity universal joints 31A, 31B include an outer joint member 34 having a plurality of linear track grooves 33 formed along the axial direction on its cylindrical inner peripheral surface, an inner joint member 36 having a plurality of linear track grooves 35 formed along the axial direction on its spherical outer peripheral surface in pairs with the track grooves 33 of the outer joint member 34, a plurality of balls 37 as torque transmission members interposed between the track grooves 33 of the outer joint member 34 and the track grooves 35 of the inner joint member 36 to transmit torque, and a cage 38 interposed between the cylindrical inner peripheral surface of the outer joint member 34 and the spherical outer peripheral surface of the inner joint member 36 to hold the balls 37.

[0037] Each outer joint member 34 comprises a cylindrical main body 39 having track grooves 33 formed on its cylindrical inner circumferential surface, and a flange 40 provided on one opening side of the cylindrical main body 39. The other opening of the cylindrical main body 39 is closed by a boot 41. The boot 41 comprises a large-diameter portion (one opening end) 41a, a small-diameter portion (the other opening end) 41b, and a bellows portion 41c connecting the large-diameter portion 41a and the small-diameter portion 41b. The large-diameter portion 41a is fitted onto a boot attachment portion 42 having a circumferential groove at the other opening of the cylindrical main body 39, and in this state is fastened by a boot band 43.

[0038] The small diameter portion 41b of the boot 41 is fitted onto a boot attachment portion 44 of the shaft S (which, unlike the conventional one shown in FIG. 9, has no groove), and in this state is fastened by a boot band 43. A retaining ring 47 is attached to the open end of the inner peripheral surface of the outer joint member 34 to prevent the internal parts P (the inner joint member 36, cage 38, balls 37, etc.) from coming off. That is, a circumferential groove 46 is formed on the open side of the inner diameter surface of the cylindrical main body 39 of the outer joint member 34, and a retaining ring 47 is attached to this circumferential groove 46.

[0039] The intermediate shaft (shaft) S comprises an intermediate large-diameter shaft portion 45a (see FIG. 2) and end-side small-diameter shaft portions 45c connected to both axial ends of the intermediate large-diameter shaft portion 45a via tapered portions 45b (see FIG. 2). Male splines 45d are formed on the end of each small-diameter shaft portion 45c, and the male splines 45d are fitted into the axial holes of the respective inner joint members 36. Female splines 36a are formed on the inner diameter surface of the axial holes of the respective inner joint members 36. Therefore, when the male splines 45d of the shaft S are fitted into the axial holes of the respective inner joint members 36, they mesh with the female splines 36a of the respective inner joint members 36.

[0040] Furthermore, a pair of retaining rings 47, 48 are attached to each of the male splines 45d at both ends of the shaft S. That is, a pair of circumferential grooves are formed in the male spline 45d, and the retaining rings 47, 48 are fitted into each of the circumferential grooves. This prevents the shaft S from coming off the inner joint member 36.

[0041] 1(a), the internal part P is slid (moved) toward the inner side of the joint (retracted state), and can be displaced from this state to a state in which the internal part P is slid (moved) toward the joint opening side (extended state) as shown in FIG. 1(b), or conversely, can be displaced from the extended state to a contracted state. At this time, the shaft S also slides (moves) toward the inner side of the joint relative to the outer joint member 4, and also slides (moves) toward the joint opening side together with the internal part P. In other words, the internal part P can reciprocate within the outer joint member 34 in the direction of arrow X (axial direction) shown in FIGS. 1(a) and 1(b).

[0042] This constant velocity universal joint has a sleeve inner ring 51 and a sleeve outer ring 52 that are fitted onto the small diameter portion 45c of the shaft S. That is, the sleeve inner ring 51 is made of a cylindrical body having, at the end opposite the internal component, a fitting portion 51a with a recessed groove into which the inner diameter side bulge 41b1 of the small diameter portion 41b of the boot 41 fits. The fitting portion 51a is interposed between the small diameter portion 45c of the shaft and the small diameter portion 41b of the boot 41, and is fastened by a boot band 43 to be fixed to the small diameter portion 41b of the boot 41. That is, the fitting portion 51a of the sleeve inner ring 51 and the small diameter portion 41b of the boot 41 are integrated, but the shaft S can reciprocate (slide) in its axial direction relative to the sleeve inner ring 51. The length of the sleeve inner ring 51 is such that the end on the internal component side (the end opposite to the fitting portion 51a in the axial direction) reaches the middle portion of the bellows portion 41c of the boot 41 in the axial direction.

[0043] The sleeve outer ring 52 is fixed to the inner joint member 36 and is made of a cylindrical body having an outer flange 52a on the inner joint member side. Therefore, with the outer flange 52a abutting against the end face on the open end side of the inner joint member 36, the outer flange 52a is fixed to the inner joint member 36 via a fastener 53 such as a hexagonal bolt. The axial length of the sleeve outer ring 52 is such that the end on the side opposite to the outer flange reaches an axial middle position of the bellows portion 41c of the boot 41.

[0044] In this case, as shown in Figures 3(b) and 4(b), a gap 55 into which the sleeve inner ring 51 is slidably fitted is formed between the sleeve outer ring 52 and the opposing shaft. That is, a circumferential cutout is provided on the inner diameter surface of the sleeve outer ring 52, and this circumferential cutout and the outer diameter surface of the small diameter portion 45c of the shaft S form the gap 55. In addition, a circumferential protrusion 56 that protrudes outward is provided on the edge of the sleeve outer ring 52 on the sleeve inner ring side.

[0045] Incidentally, since the shaft S needs to slide (reciprocate) relative to the sleeve inner ring 51 in its axial direction, there is a clearance fit between the sleeve inner ring 51 and the shaft S. In contrast, the shaft S does not slide (reciprocate) relative to the sleeve outer ring 52, and since the sleeve outer ring 52 and the shaft S need to be integrated, it is preferable that the sleeve outer ring 52 and the shaft S be an interference fit or a transition fit; however, since the outer flange portion 52a of the sleeve outer ring 52 is fixed (secured) to the inner joint member 36, there may be a clearance fit between the sleeve outer ring 52 and the shaft S instead of an interference fit or a transition fit. Furthermore, since the sleeve outer ring 52 and the sleeve inner ring 51 need to slide relative to each other in the axial direction, a clearance fit with the gap portion 55 of the sleeve inner ring 51 is required.

[0046] 1(a) and 3(a) and 3(b), when the internal part P is slid (moved) toward the rear of the joint (in a contracted state), the end of the anti-fitting portion of the sleeve inner ring 51 is fitted into the gap 55 by a predetermined distance L1. In this state, no compressive or tensile force acts on the boot 41, and the bellows portion 41c of the boot 41 maintains its natural state.

[0047] From this state, as shown in FIG. 1(b), when the internal part P slides (moves) in the direction of arrow A toward the joint opening (stretched state), the sleeve outer ring 52 also moves in the direction of arrow A as the internal part P slides. As shown in FIG. 1(b) and 4(a) and 4(b), the sleeve inner ring 51 is inserted into the gap 55 by a predetermined distance L2. In this state, even if the shaft S moves, the sleeve inner ring 51 does not move, and therefore the small-diameter portion 41b of the boot 41 does not move either. Therefore, no compressive or tensile force acts on the boot 41, and the bellows portion 41c of the boot 41 maintains its natural state. When the length of the gap 55 is L, L - L2 = L3 > 0. That is, in the stretched state, the edge of the non-engagement portion of the sleeve inner ring 51 does not contact the bottom of the gap. It should be noted that L3 indicates the length of the portion of the gap 55 where the sleeve inner ring 51 is not fitted (the remaining length) in the stretched state.

[0048] In this way, the boot inner fitting portion of the sleeve inner ring 51 (the portion of the sleeve inner ring excluding the fitting portion 51a) is maintained fitted into the gap portion 55, and the sleeve outer ring 52 and the sleeve inner ring 51 always have an overlapping portion K. That is, even if the shaft S slides in the direction of arrow A from the state shown in Fig. 1(a) to the state shown in Fig. 1(b), or conversely, if the shaft S slides in the direction of arrow B from the state shown in Fig. 1(b) to the state shown in Fig. 1(a), the overlapping portion K is formed although the axial length is different.

[0049] According to the constant velocity universal joint of the present invention, the shaft S is connected to the inner joint member 36 of the internal part P, so when the internal part P reciprocates between the joint opening side and the joint inner side with respect to the outer joint member 34, the shaft S also reciprocates in response to this reciprocating movement. However, because the shaft S is slidably fitted into the inner ring of the sleeve, the small diameter portion of the boot 41 does not slide in response to the sliding of the shaft S, and therefore no displacement of the boot 41 occurs.

[0050] Furthermore, the shaft S inside the boot is fitted into the sleeve outer ring 52 on the internal component side, and the small diameter side of the boot 41 is fitted into the sleeve inner ring 51, and moreover, the sleeve outer ring 52 and the sleeve inner ring 51 always have an overlapping portion K. Therefore, the shaft S inside the boot is not exposed inside the boot, and grease G does not get in between the sleeve outer ring 52 and the shaft S or between the sleeve inner ring 51 and the shaft S, effectively preventing grease B from leaking out of the boot.

[0051] Furthermore, as the shaft S slides, the small diameter portion 41b of the boot 41 does not slide, and no displacement occurs in the boot 41. This allows for a longer lifespan of the boot 41. Also, as described above, it is possible to effectively prevent the grease G from leaking out of the boot, so that the grease G does not splash onto surrounding components or become reduced in the joint body or inside the boot, allowing for excellent lubrication performance to be maintained over the long term, and the possibility of impairing the durability of the joint due to poor lubrication is extremely reduced.

[0052] By providing a circumferential protrusion 56 on the sleeve outer ring 52, this circumferential protrusion 56 acts as a so-called grease return, effectively preventing grease G adhering to the sleeve outer ring 52 from flying into the boot due to centrifugal force and flowing out of the boot.

[0053] 5(a) and 5(b) show a modified example, in which a seal member 57 is disposed on the edge of the sleeve outer ring 52 on the sleeve inner ring 51 side, to seal the gap between the sleeve outer ring 52 and the sleeve inner ring 51. That is, the seal member 57, which is a sealing device such as an oil seal or O-ring, is disposed on the edge of the sleeve outer ring 52 on the small diameter side of the boot 41, to seal the gap between the edge and the outer diameter surface of the sleeve inner ring 51. Note that other configurations of the constant velocity universal joint shown in FIGS. 5(a) and 5(b) are the same as those of the constant velocity universal joint shown in FIGS. 1(a) and 1(b), and therefore the same members are designated by the symbols shown in FIGS. 1(a) and 1(b), and their description will be omitted.

[0054] The constant velocity universal joint shown in Figures 5(a) and 5(b) can achieve the same effects as the constant velocity universal joint shown in Figures 1(a) and 1(b). Furthermore, although the sleeve outer ring 52 does not have a circumferential protrusion 56, the provision of the seal member 57 prevents grease G from entering between the sleeve outer ring 52 and the sleeve inner ring 51, effectively preventing grease G from leaking out of the boot.

[0055] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible. The constant velocity universal joint may be a cross groove type constant velocity universal joint (LJ) or a tripod type constant velocity universal joint (TJ), etc. When a cross groove type constant velocity universal joint is used, it may be a float type or a non-float type, and when a tripod type constant velocity universal joint is used, it may be a single roller type or a double roller type.

[0056] As a power transmission mechanism, either one of the constant velocity universal joints may be a fixed constant velocity universal joint. The fixed constant velocity universal joint may be a Birrfield type fixed constant velocity universal joint or an undercut-free type fixed constant velocity universal joint. Furthermore, the number of peaks and valleys of the bellows portion 41c of the boot 41 is not limited to that in the embodiment, and the number may be increased or decreased as desired. [Explanation of symbols]

[0057] 34 Outer joint member 36 Inner joint member 37 Torque transmission member (ball) 41a Large diameter portion (one open end) 41b Small diameter portion (the other open end) 41b1 Inner bulge 41c Bellows 51 Sleeve inner ring 52 Sleeve outer ring 52a Outer flange 55 Gap K overlapping region P internal parts S shaft

Claims

1. a constant velocity universal joint comprising an outer joint member, an inner joint member, and a torque transmission member interposed between the outer joint member and the inner joint member, an internal part having the inner joint member and the torque transmission member housed in the outer joint member so as to be axially slidable, a shaft is connected to the inner joint member of the internal part, one open end is attached to an opening of the outer joint member, and the other open end is attached to the shaft, thereby sealing the interior of the joint, an inner sleeve ring that is housed in the boot with its end opposite to the inner component interposed between the inner diameter portion of the other open end of the boot and the outer diameter surface of the shaft, and into which the shaft is fitted so as to be slidable in the axial direction; an outer sleeve ring, the end of which is opposite to the inner sleeve ring and is fixed to the inner joint member of the internal component, and into which the shaft is fitted; A constant velocity universal joint characterized in that a gap is formed between the sleeve outer ring and the shaft facing it, into which the sleeve inner ring is slidably fitted, and the boot inner fitting portion of the sleeve inner ring is maintained fitted into the gap, so that the sleeve outer ring and the sleeve inner ring always have an overlapping portion.

2. 2. The constant velocity universal joint according to claim 1, wherein a circumferential projection projecting outwardly is provided on an edge of the outer sleeve ring on the inner sleeve ring side.

3. 2. A constant velocity universal joint according to claim 1, wherein a seal member for sealing the gap between said outer sleeve ring and said inner sleeve ring is disposed on an edge portion of said outer sleeve ring on the inner sleeve ring side.

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